1. Field of the Invention
The present invention is related to a method for the preparation of self-assembled silicon nanotubes (SiNTs), in particular, to a method for the synthesis of self-assembled SiNTs from inorganic solution (hydrothermal solution).
2. Description of the Related Art
Although the difficulty in the synthesis of SiNTs is widely attributed to the sp3 hybridization in silicon, the possibility of the existence of SiNTs has been suggested theoretically. The preparation of SiNTs, especially self-assembled SiNTs is still very challenging at present. Great interest has focused on carbon nanotubes (CNTs) owing to their excellent properties, and many researchers in the world are attempting to prepare self-assembled SiNTs. Recently SiNTs were prepared using a template method respectively by Jeong and his coworkers in Sungkyunkwan University, and Sha and his coworkers in Zhejiang University. The corresponding research results were published in Advanced Materials (Adv Mater), which is a famous international journal in the field of materials.
SiNTs with an outer diameter of less than 100 nm were synthesized by Jeong and his coworkers using alumina templates. The templates were brought into a molecular beam epitaxy (MBE) chamber where the chamber was evacuated to a pressure of 5×10−10 Torr. The Si atoms/clusters were sputtered for 10 min by an electron-beam evaporator. The temperature of alumina templates was maintained at 400° C. After the deposition, the sample was further heat treated at 600° C. or 750° C. under ambient conditions for oxidation.
SiNTs with an outer diameter of less than 100 nm were also fabricated by Sha and his coworkers using a nanochannel Al2O3 (NCA), silane as the silicon source and gold as the catalyst at 620° C. and 1450 Pa by a chemical vapor deposition (CVD) process.
Although SiNTs have been prepared by the alumina template and NCA, the SiNTs were formed in the inner wall of templates by aggregation and not by self-assembled growth of the elemental Si. Therefore SiNTs obtained by the templates are not really self-assembled SiNTs.